The present invention relates to the connection of a point on an electronics card to a metal substrate which carries the said card.
At present, there are essentially three known techniques for making such a connection.
One of them consists of making a soldered joint using a solder paste deposited on that face of the card which is intended to be opposite the metal substrate, the latter having previously been treated with a finish which can be soldered (nickel, for example).
However, particularly because of the finishing treatment, this technique is expensive.
Another technique consists of using a rivet which passes through both the card and the metal substrate.
This technique is not satisfactory either. In particular, it does not allow an impervious connection and requires an additional step for forming a seal, which is formed by depositing an adhesive and polymerising, for example. Furthermore, carrying out this riveting requires two machining operations: one for piercing and the other for recessing the riveting hole.
Consequently, the number of additional operations required by the riveting technique makes this technique impracticable.
Finally, another technique consists in driving a metal pin into the substrate, this pin passing through the electronics card, the substrate having previously been machined to the dimensions of the said pin.
However, this technique also has drawbacks. In particular, it is not an easy matter to manipulate the pin, and the dimensions of the latter can be altered during manipulation. In addition, this technique requires a hole to be pierced with high precision, this hole not opening out in the substrate. Consequently, this technique is not simple to implement.
The connection techniques using metal pins or rivets also have other disadvantages common to them.
They require the electronics card to be placed under stress around the rivet or pin, which mechanically weakens the said card.
Moreover, the electrical contact--which is provided solely by the mechanical pressure itself--is not thereby very reliable.
Equally, the additional thicknesses of the rivet or of the pin on the electronics card prove to be inconvenient for the operations of mounting the SMD components.